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@cf-wasm/og

Generate Open Graph Images dynamically from HTML/CSS without a browser.

Powered by @vercel/og.

Warning

Breaking changes may be introduced without following semantic versioning.
Please note that this package may undergo breaking changes between versions without adhering strictly to semantic versioning (SemVer). While efforts will be made to minimize disruptions, it's recommended to review release notes carefully before upgrading to a new version. We apologize for any inconvenience this may cause and appreciate your understanding.

Installation

npm install @cf-wasm/og       # npm
yarn add @cf-wasm/og          # yarn
pnpm add @cf-wasm/og          # pnpm

Usage

  • Cloudflare Workers / Pages (Esbuild):

    import { ImageResponse } from "@cf-wasm/og";

  • Next.js Edge Runtime (Webpack):

    import { ImageResponse } from "@cf-wasm/og/next";

  • Node.js (file base):

    import { ImageResponse } from "@cf-wasm/og/node";

Documentation

Cloudflare Workers/Pages

If you are using Cloudflare Workers/Pages, you must set the execution context as shown:

import React from "react";
import { ImageResponse, cache } from "@cf-wasm/og";

export default {
  fetch(req, env, ctx) {
    // Set execution context
    cache.setExecutionContext(ctx);

    return new ImageResponse(<>Hello World!</>);
  }
} satisfies ExportedHandler;

Font Loaders

You can load Google fonts and Custom fonts with ease using GoogleFont and CustomFont classes respectively:

import React from "react";
import { ImageResponse, GoogleFont, CustomFont, cache } from "@cf-wasm/og";

export default {
  fetch(req, env, ctx) {
    cache.setExecutionContext(ctx);

    return new ImageResponse(
      (
        <div
          style={{
            display: "flex",
            flexDirection: "column",
            alignItems: "center",
            justifyContent: "center",
            width: "100%",
            height: "100%"
          }}
        >
          <p>Text with Default font</p>
          <p style={{ fontFamily: "Inclusive Sans" }}>Text with Google font</p>
          <p style={{ fontFamily: "JetBrains Mono" }}>Text with Custom font</p>
        </div>
      ),
      {
        fonts: [
          // Using Google font loader
          new GoogleFont("Inclusive Sans"),
          // Using Custom font loader
          new CustomFont("JetBrains Mono", () =>
            fetch(
              "https://github.com/JetBrains/JetBrainsMono/raw/master/fonts/ttf/JetBrainsMono-Regular.ttf"
            ).then((res) => res.arrayBuffer())
          )
        ]
      }
    );
  }
} satisfies ExportedHandler;

Default font

You can set global default font using GoogleFont or CustomFont classes:

import React from "react";
import {
  ImageResponse,
  CustomFont,
  GoogleFont,
  defaultFont,
  cache
} from "@cf-wasm/og";

// By using Google font loader
defaultFont.set(new GoogleFont("Merriweather"));

// or
// By using Custom font loader
defaultFont.set(
  new CustomFont("JetBrains Mono", () =>
    fetch(
      "https://github.com/JetBrains/JetBrainsMono/raw/master/fonts/ttf/JetBrainsMono-Regular.ttf"
    ).then((res) => res.arrayBuffer())
  )
);

export default {
  fetch(req, env, ctx) {
    cache.setExecutionContext(ctx);

    // It should render with JetBrains Mono font
    return new ImageResponse(<>Hello World!</>);
  }
} satisfies ExportedHandler;

You can set default font using defaultFont option:

import React from "react";
import { ImageResponse, GoogleFont, cache } from "@cf-wasm/og";

export default {
  fetch(req, env, ctx) {
    cache.setExecutionContext(ctx);

    return new ImageResponse(<>Hello World!</>, {
      // Set default font
      defaultFont: new GoogleFont("Merriweather")
    });
  }
} satisfies ExportedHandler;

SVG format

By default ImageResponse renders to PNG but you can use format option to render to SVG:

import React from "react";
import { ImageResponse, cache } from "@cf-wasm/og";

export default {
  fetch(req, env, ctx) {
    cache.setExecutionContext(ctx);

    return new ImageResponse(<>Hello World!</>, {
      // Set format
      format: "svg"
    });
  }
} satisfies ExportedHandler;

Render HTML

The @cf-wasm/og/html-to-react submodule provides a function t which can be used to transform html to ReactElement making it possible to render html as well:

import { ImageResponse, cache } from "@cf-wasm/og";
import { t } from "@cf-wasm/og/html-to-react";

export default {
  fetch(req, env, ctx) {
    cache.setExecutionContext(ctx);

    const html = `<div style="display: flex; flex-direction: column; align-items: center; justify-content: center; width: 100%; height: 100%;">
        <p>Renders HTML</p>
        <p>Hello World!</p>
      </div>`;

    return new ImageResponse(t(html));
  }
} satisfies ExportedHandler;

render function

You can also use render function instead of ImageResponse to catch errors or for other use cases:

import React from "react";
import { render, cache } from "@cf-wasm/og";

export default {
  async fetch(req, env, ctx) {
    cache.setExecutionContext(ctx);

    try {
      const { image } = await render(<>Hello World!</>).asPng();

      return new Response(image, {
        headers: {
          "Content-Type": "image/png"
        }
      });
    } catch {
      return new Response("Not found", {
        status: 404
      });
    }
  }
} satisfies ExportedHandler;

Examples

Following are some examples for using this library:

Cloudflare Workers

If you are using Cloudflare Workers, you can use it as shown below:

// src/index.tsx
import React from "react";
import { ImageResponse, GoogleFont, cache } from "@cf-wasm/og";

export default {
  async fetch(req, env, ctx) {
    // Make sure to set the execution context
    cache.setExecutionContext(ctx);

    const { searchParams } = new URL(req.url);
    const parameters = Object.fromEntries(searchParams.entries());

    return new ImageResponse(
      (
        <div
          style={{
            display: "flex",
            flexDirection: "column",
            width: "100%",
            height: "100%",
            alignItems: "center",
            justifyContent: "center",
            backgroundColor: "#6f90ab",
            fontSize: "2rem",
            color: "#fff"
          }}
        >
          <span>Noto Sans (Default Font)</span>
          <span
            style={{
              fontFamily: "JetBrains Mono"
            }}
          >
            JetBrains Mono (using GoogleFont class)
          </span>
          <span>These are emojis: 😎🌩️</span>
          <span
            style={{
              fontFamily: "JetBrains Mono"
            }}
          >
            Parameters: {JSON.stringify(parameters)}
          </span>
        </div>
      ),
      {
        fonts: [new GoogleFont("JetBrains Mono")],
        emoji: "fluent"
      }
    );
  }
} satisfies ExportedHandler;

Warning

If you are using @cf-wasm/og on Cloudflare Workers, you may hit the CPU time limit as well as the 1MiB script size limit (Workers Free Plan). Even when using the original project @vercel/og on Cloudflare Pages, you hit the CPU time limit.

Next.js (App Router)

If you are using Next.js (App router) with edge runtime, you can use it as shown below:

// (src/)app/api/og/route.tsx
import React from "react";
import { type NextRequest } from "next/server";
import { ImageResponse, GoogleFont } from "@cf-wasm/og/next";

export const runtime = "edge";

export function GET(req: NextRequest) {
  const { searchParams } = req.nextUrl;
  const parameters = Object.fromEntries(searchParams.entries());

  return new ImageResponse(
    (
      <div
        style={{
          display: "flex",
          flexDirection: "column",
          width: "100%",
          height: "100%",
          alignItems: "center",
          justifyContent: "center",
          backgroundColor: "#6f90ab",
          fontSize: "2rem",
          color: "#fff"
        }}
      >
        <span>Noto Sans (Default Font)</span>
        <span
          style={{
            fontFamily: "JetBrains Mono"
          }}
        >
          JetBrains Mono (using GoogleFont class)
        </span>
        <span>These are emojis: 😎🌩️</span>
        <span
          style={{
            fontFamily: "JetBrains Mono"
          }}
        >
          Parameters: {JSON.stringify(parameters)}
        </span>
      </div>
    ),
    {
      fonts: [new GoogleFont("JetBrains Mono")],
      emoji: "fluent"
    }
  );
}

Next.js (Pages Router)

If you are using Next.js (Pages router) with edge runtime, you can use it as shown below:

// (src/)pages/api/og.tsx
import React from "react";
import { type NextRequest } from "next/server";
import { ImageResponse, GoogleFont } from "@cf-wasm/og/next";

export const config = {
  runtime: "edge"
};

export default async function handler(req: NextRequest) {
  const { searchParams } = req.nextUrl;
  const parameters = Object.fromEntries(searchParams.entries());

  return new ImageResponse(
    (
      <div
        style={{
          display: "flex",
          flexDirection: "column",
          width: "100%",
          height: "100%",
          alignItems: "center",
          justifyContent: "center",
          backgroundColor: "#6f90ab",
          fontSize: "2rem",
          color: "#fff"
        }}
      >
        <span>Noto Sans (Default Font)</span>
        <span
          style={{
            fontFamily: "JetBrains Mono"
          }}
        >
          JetBrains Mono (using GoogleFont class)
        </span>
        <span>These are emojis: 😎🌩️</span>
        <span
          style={{
            fontFamily: "JetBrains Mono"
          }}
        >
          Parameters: {JSON.stringify(parameters)}
        </span>
      </div>
    ),
    {
      fonts: [new GoogleFont("JetBrains Mono")],
      emoji: "fluent"
    }
  );
}